Circuit and method for processing image abnormality caused by power supply

ABSTRACT

A method for processing an image abnormality caused by power supply is provided, which is used in a digital image-capturing apparatus. The method can be described as follows. First, power of the digital image-capturing apparatus is turned on. Next, a line data of an image being captured is started to be transmitted, wherein the line data has a dummy pixel region and an effective pixel region, and the dummy pixel region is first transmitted, and then a plurality of pixel data of the effective pixel region is transmitted. Next, a horizontal driving current to be input to a horizontal driver is processed, so that the horizontal driving current substantially approaches a stable state before the effective pixel region is output. Finally, the above steps are repeated for continually transmitting a next line data of the image being captured until the image of the digital image-capturing apparatus is completely transmitted.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 98107134, filed on Mar. 5, 2009. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image-capturing technique. Moreparticularly, the present invention relates to a technique forprocessing image abnormality caused by power supply.

2. Description of Related Art

With development of digital still camera (DSC) techniques, and progressof digital signal processing techniques, besides a high resolution, ahigh-ISO performance of the DSC is also pursued in the market. However,technique problems are also generated. To achieve the high resolution,more sensing pixels are required, so that a larger current is requiredto transmit data (image). In case that the high-ISO is required and thesensing pixels are not increased, an analogue gain has to be increased.Under such a strict condition, a speed of a transient response of apower system can also influence an image quality.

FIG. 1 is a block diagram illustrating a commonly used DSC system.Referring to FIG. 1, the DSC 90 includes a digital signal processor(DSP) 100, an analogue front end (AFE) unit 96, a charge coupled device(CCD) 98, a low drop-out (LDO) voltage regulator 94, and a power supply92, wherein the LDO voltage regulator 94 can also be a DC/DC converter.A function of the LDO voltage regulator 94 or the DC/DC converter 94 isused for supplying power to the circuit units. The DSP 100 controlsoperations of the whole system (including operations of the AFEprocessing unit 96 and the CCD 98). When the AFE processing unit 96receives a horizontal sync signal Hsync from the DSP 100, the AFEprocessing unit 96 outputs a horizontal and a vertical control signalsΦ_(H) and Φ_(V) to the CCD 98, and simultaneously receives an outputsignal OS from the CCD 98. The image data of the output signal OS isprocessed by an ADC/AGC 116 and an ADC 110, and is converted from ananalogue signal to a digital signal, and then is transmitted to the DSP100. This is an image processing process of the DSC 90. The DSP 100 canalso control a lens driver 124 to interactively control a lens module126.

Other elements such as memory devices RAM 104 and ROM 106, and a LCDpanel 102 are used for displaying images. Further, the AFE processingunit 96 further includes a timing generator (TG) 108, and the TG 108respectively generates a horizontal clock and a vertical clock to ahorizontal driver 112 and a vertical driver 114. The LDO voltageregulator 94 provides a horizontal voltage V_(ΦH) and a horizontalcurrent I_(ΦH) to the horizontal driver 112 for driving the image onhorizontal scan lines. The image sensed by the CCD 98 is output by linedata one after another.

Since at an initial stage, the horizontal current I_(ΦH) has an inrushnoise of transient oscillation, a quality of the front part of theoutput image is influenced. For example, vertical stripes, horizontalstripes, ghosts, pits, etc., may all severely influence the quality ofthe image.

FIG. 2 is a timing diagram of a conventional image transmission. FIG. 3is an amplified diagram of an initial section 140 during theconventional image transmission of FIG. 2. Referring to FIG. 2, FIG. 2is a timing diagram of the horizontal sync signal Hsync, the horizontalcontrol signal Φ_(H), the horizontal voltage V_(ΦH) and the horizontalcurrent I_(ΦH), etc. The horizontal control signal Φ_(H) is a horizontalshift clock. When the AFE processing unit 96 outputs the horizontalcontrol signal Φ_(H) to the CCD 98, a transient high current about 100mA can be generated. The horizontal driver 112 used for outputting thehorizontal control signal Φ_(H) may have an unstable current and voltagedue to such transient high current, so that the analogue signal of theimage of the CCD 98 at the initial section of a left part can beinterfered to having noises such as vertical stripes, etc. Such unstablecurrent and voltage phenomenon is shown as the initial section 140, andan amplified diagram thereof is shown as FIG. 3.

Referring to FIG. 3, by amplifying the initial section 140 that thehorizontal control signal Φ_(H) is initially transmitted, it is obviousthat when the current is unstable, the initial section 140 exceeds adummy pixel region 142 of a line data of a horizontal image, and some ofpixel regions 146 belonged to the effective pixel region 144 has beentransmitted. Namely, since the current is unstable at the initialsection, bad pixels at the pixel region 146 can influence the imagequality of a left part (an initial position) of the CCD image thatcorresponds to the region 146, which is a main reason that causes thenoise.

Therefore, at least the aforementioned problem of image noise has to beresolved.

SUMMARY OF THE INVENTION

The present invention is directed to a method and a circuit forprocessing image abnormality caused by power supply, so as to at leastresolve a problem of front-end noise of an image.

The present invention provides a method for processing an imageabnormality caused by power supply, which is used in a digitalimage-capturing apparatus. The method can be described as follows.First, power of the digital image-capturing apparatus is turned on.Next, a line data of an image being captured is started to betransmitted, wherein the line data has a dummy pixel region and aneffective pixel region, and the dummy pixel region is first transmitted,and then a plurality of pixel data of the effective pixel region istransmitted. Next, a horizontal driving current to be input to ahorizontal driver is processed, so that the horizontal driving currentsubstantially approaches a stable state before the effective pixelregion is output. Finally, the above steps are repeated for continuallytransmitting a next line data of the image being captured until theimage of the digital image-capturing apparatus is completelytransmitted.

The present invention provides a circuit for processing an imageabnormality caused by power supply, which is used in a digitalimage-capturing apparatus. The circuit includes a digital signalprocessor (DSP), an analogue front-end (AFE) processing unit, animage-capturing unit, a voltage current regulation unit, a power supplycircuit and an emulative device. The AFE processing unit includes ahorizontal driver, and is mutually communicated with the DSP, whereinthe DSP or the AFE processing unit outputs a pulse-width modulation(PWM) signal. The image-capturing unit is mutually communicated with theDSP, and is driven by the horizontal driver. The voltage currentregulation unit at least provides a voltage and a current to the AFEprocessing unit. The power supply circuit provides power to the voltagecurrent regulation unit. The emulative device is connected to an outputterminal of the voltage current regulation unit. During a predeterminedtime section before the voltage current regulation unit provides thevoltage and the current to the AFE processing unit, the emulative deviceis in a turned-on state under control of the PWM signal. Otherwise, theemulative device is in a turned-off state.

In order to make the aforementioned and other features and advantages ofthe present invention comprehensible, several exemplary embodimentsaccompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram illustrating a DSC system.

FIG. 2 is a timing diagram of a conventional image transmission.

FIG. 3 is an amplified diagram of an initial section 140 during aconventional image transmission of FIG. 2.

FIG. 4 is a schematic diagram illustrating a mechanism of processing ahorizontal shift clock Φ_(H) according to an embodiment of the presentinvention.

FIG. 5 is an amplified diagram of a region of FIG. 4.

FIG. 6 is a block diagram of a circuit for processing image abnormalitycaused by power supply according to an embodiment of the presentinvention and a mechanism of FIG. 4.

FIG. 7 is a flowchart illustrating a method for processing imageabnormality caused by power supply according to an embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

The present invention provides a circuit and a method for at leastprocessing image abnormality caused by power supply. A plurality ofembodiments is provided below to describe the present invention, thoughthe present invention is not limited to the provided embodiments.

In the present invention, a horizontal shift clock Φ_(H) is processed.For example, by setting an emulative device, using a LDO voltageregulator or a DC/DC converter with a fast transient response, or usingan inductor and a capacitor, a transient response curve of the LDOvoltage regulator or the DC/DC converter can be modified.

FIG. 4 is a schematic diagram illustrating a mechanism of processing thehorizontal shift clock Φ_(H) according to an embodiment of the presentinvention. FIG. 5 is an amplified diagram of a region of FIG. 4. FIG. 6is a block diagram of a circuit for processing image abnormality causedby power supply according to an embodiment of the present invention anda mechanism of FIG. 4. Referring to FIGS. 4-6, in the presentembodiment, an emulative device 202 is applied. For example, in adriving circuit of a DSC system applying a CCD 214, a DSP 200 functionsas the DSP 100 of FIG. 1, which is used for controlling a digitalimage-capturing apparatus. In allusion to the horizontal shift clockΦ_(H), the emulative device 202 is added to a horizontal driver 210 ofan AFE processing unit 208 to serve as a load device. The emulativedevice 202 can be implemented by a simple circuit, for example, can beimplemented by a switch and a resistor, wherein the switch can be, forexample, implemented by a semiconductor transistor such as a bipolarjunction transistor (BJT) or a metal oxide semiconductor (MOS)transistor. The transistor can be turned on or turned off in response toa control signal to serve as a switch, which is easy to be controlled.In the present embodiment, the BJT is taken as an example, and the BJTis turned on/off in response to a PWM signal 212. The PWM signal 212 is,for example, generated by the DSP 200. Though, the AFE processing unit208 can also generate the PWM signal 212. In other words, the DSP 200 orthe AFE processing unit 208 can all generate the PWM signal 212, or anequivalent PWM signal can be generated by other units. One end of theemulative device is couple to an input terminal of the AFE processingunit 208, and another end thereof is coupled to the ground. The inputterminal of the AFE processing unit 208 receives a horizontal voltageV_(ΦH) and a horizontal current I_(ΦH) from the LDO voltage regulator206. A power supply 204 provides a system voltage to the LDO voltageregulator 206. The input terminal of the AFE 208 can also be coupled tothe DC/DC converter.

According to FIG. 4, when the horizontal sync signal Hsync is activated,the horizontal shift clock Φ_(H) is not immediately generated. Since theemulative device 202 is applied, the emulative device 202 can be turnedon by the PWM signal during a time section A, so that the horizontalvoltage V_(ΦH) and the horizontal current I_(ΦH) can reach a stablestate before the horizontal shift clock Φ_(H) is transmitted. By suchmeans, a transient high current vibration of the LDO voltage regulator206 can be reduced. During a time section B, the emulative device 202 isturned off, so that a line data of an image is started to be transmittedaccording to the horizontal shift clock Φ_(H). An amplified diagram ofthe time section A is shown in FIG. 5.

According to FIG. 5, before the effective pixel region 160 istransmitted by the output signal OS of the CCD 214, an inrush currentnoise can be generated ahead due to a current generated by a loadresistor, so that the noise of the left part (the initial position) ofthe CCD image can be effectively reduced. Therefore, since a dummy pixelregion 150 is still located in front of the effective pixel region 160,a width of the PWM signal can be suitably matched.

In present embodiment, the emulative device 202 is applied toeffectively eliminate the noise of the left part of the CCD image. Theemulative load device used in allusion to the horizontal shift clockΦ_(H) can meliorate a general power supply system, and such emulativedevice has no difference in an effect of reducing the noise as devicecharacteristics are varied, and for different combinations of sensorsand power supply systems, modifications can be effectively achieved byonly performing easy calculations and slightly adjusting the emulativeload.

FIG. 7 is a flowchart illustrating a method for processing imageabnormality caused by power supply according to an embodiment of thepresent invention. Referring to FIG. 7 and FIG. 6, in step S700, poweris turned on to activate the system. In step S702, a line data of a CCDimage is started to be transmitted. In step S704, a virtual loadmechanism is activated. Namely, the emulative device 202 is turned on.In step S706, the emulative device 202 is maintained in a turned-onstate until the horizontal driver 210 starts to transmit the horizontalshift clock Φ_(H), and then the emulative device 202 is turned off untila line data of the CCD image is transmitted. In step S708, a next linedata is continually transmitted and the above steps are repeated untilthe image is completely transmitted.

In other words, in the present invention, a horizontal driving currentto be input to a horizontal driver is processed, so that the horizontaldriving current substantially approaches a stable state before theeffective pixel region is output. Regarding a general method, amechanism thereof is similar to that of the method shown in FIG. 7, bywhich the horizontal driving current is also processed, so that itsubstantially approaches a stable state before the effective pixelregion is output. Since the current is related to the voltage,processing the horizontal current is equivalent to processing thehorizontal voltage, and if the current is stable, it also representsthat the voltage is stable. Similarly, if the voltage is stable, it alsorepresents the current is stable.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A circuit for processing an image abnormality caused by power supply,used in a digital image-capturing apparatus, comprising: a digitalsignal processor (DSP); an analogue front-end (AFE) processing unit,comprising a horizontal driver, and mutually communicated with the DSP,wherein the DSP or the AFE processing unit outputs a pulse-widthmodulation (PWM) signal; an image-capturing unit, mutually communicatedwith the DSP, and driven by the horizontal driver; a voltage currentregulation unit, at least providing a voltage and a current to the AFEprocessing unit; a power supply circuit, providing power to the voltagecurrent regulation unit; and a dummy loading device that bears an inrushcurrent noise of the current, connected to an output terminal of thevoltage current regulation unit, wherein during a predetermined timesection just before a start of transmitting a horizontal shift clock bythe AFE to the image-capturing unit, the dummy loading device is set ata turned-on state under control of the PWM signal within thepredetermined time section, and the dummy loading device is set at aturned-off state other than the predetermined time section whereby thecircuit processes an image abnormality caused by the power supply. 2.The circuit for processing an image abnormality caused by power supplyas claimed in claim 1, wherein the dummy loading device comprising: aload; a semiconductor switch device, connected to the load to form aseries circuit, the series circuit having a first terminal beingconnected to an input terminal of the horizontal driver, and a secondterminal being connected to ground, and the semiconductor switch devicebeing controlled by the PWM signal.
 3. The circuit for processing animage abnormality caused by power supply as claimed in claim 2, whereinthe load is a resistor.
 4. The circuit for processing an imageabnormality caused by power supply as claimed in claim 1, wherein thevoltage current regulation unit comprises a low drop-out (LDO) voltageregulator or a DC/DC converter.
 5. The circuit for processing an imageabnormality caused by power supply as claimed in claim 1, wherein thehorizontal driver of the AFE processing unit provides a horizontal clockto the image-capturing unit, so that the image-capturing unit transmitsan image data being captured.
 6. The circuit for processing an imageabnormality caused by power supply as claimed in claim 5, wherein whenthe dummy loading device is set at the turned-on state, the currentoutput from the voltage current regulation unit first flows into thedummy loading device, so that the dummy loading device bears an inrushcurrent noise of the current.